A profile drag is the largest drag that the athletes encounter in water. The profile drag is influenced by a project area, which is seen from an anterior view of the traveling direction, of the athlete. Therefore, keeping a posture of the athlete parallel to water surface as far as possible is advantageous in order to reduce the profile drag. That is, it is desirable to prevent positions of the waist, knees and toes of the athlete from sinking relative to a position of the head of the athlete during swimming, and to keep the whole body posture parallel and straight to water surface as far as possible.
However, the athlete's posture tends to be unstable because of the action of gravity and buoyancy applying to the axis of the athlete. Meanwhile, the lower body has a greater bone density and a greater muscle mass than the upper body, so the lower body is easier to sink in water than the upper body.
The following first and second patent documents are disclosed based on the above viewpoint.
First patent document: Japanese Patent Laid Open No. 2001-32104
Second patent document: Japanese Patent Laid Open No. 2001-262409
Third patent document: Japanese Patent Laid Open No. 2003-129310
The swimwear disclosed in the Japanese Patent Laid Open No. 2001-32104 is formed of a flexible clothing fabric and covers continuously over the waist and thighs of the wearer, thereby aiming at preventing a body part from the waist to legs from sinking in water.